It was developed by Maxwell Atchisson, and was developed priorly in 1972. It is capable of firing 300 rounds per minute.
(5 every second) Not only does the gun have a rapid fire rating, but is able to go as far as a normal assualt rifle.

It is capable of carrying 8 shells, with a drum barrel, 20 shells.
It can carry 3 types of ammunition: Buckshot, Frag-12 rounds, or Slugs.

Because of it's power, it is widely used in modern Military combat, and it now produced by the Military Police Systems Inc.

A Recent 2005 Model (Military Police Systems, or the MPS model for short,) has been issued and carries a slimer, lightweight look.

The gun weighs 5.2 Kgs with 8 shells, 7.3 with a drum barrel.

In other random events, the gun was featured on a 2007 episode of Future Weapons.

SWAT Member 1: So I recently heard you did a raid with the new AA-12 model.

SWAT Member 2: Oh hell yeah dude! They were packing heat, but before anyone of em' could fire at me, the whole damn room was covered in bullets.